Feb 27, 2004

Stephen Dawson has some comments on setting
calibration levels
for home theater systems. He brings up the point that the
normal HT peak level of 105 dB applies per channel. Unless I’m reading
that wrong, thats a total peak level of 112 dB, not including the +10 dB
(bandlimited) LFE channel. Ouch.

DARPA and NASA are trying to
eliminate sonic booms
associated with supersonic aircraft: “DARPA and
NASA will now work to not just reduce the boom, but eliminate it.”

Ars Technica has posted their
Portable headphone roundup
which gives subjective impressions of several popular headphone models.
They’ve included the reviews of the Etymotic Research ER-6 and ER-4P
earphones which have received rave reviews around the web.

Of course this reminds me of something I’ve been putting off for quite some
time: I was given a pair of the Bose QC-1 QuietComfort active noise reduction
(ANR) headsets as a
farewell gift when I left my last jobs (thanks again!). I’ve been meaning
to write a full-blown review including subjective impressions and
measurement results, but I just haven’t had the time.

Until I do get a chance to make a full report, I’ll leave you with these
impressions:

The ANR works very well for steady, low-frequency sounds. Mechanical sounds
(such as trucks idling outdoors or a washing machine in the
next room) are rendered nearly inaudible. As would be expected, the
ANR is not nearly as effective reducing transient
and high-frequency sounds, but the closed ear cups
provide some reduction these sounds.

I had a chance
to use the headphones on a 777 during an international flight. I was seated
behind the wings, and the headphones helped make the flight bearable. I found myself
just using the headphones (without listening to music) for the
noise reduction benefits.

The headphones are powered by 2 AA batteries. I probably
use the headphones for 15-20 minutes per day on average. At this rate, the batteries
last about 6 months.

Sound quality is pretty good, but not spectacular. As a point of reference,
I would rate the sound quality of the Bose headphones below that of the
Grado SR60’s, but certainly above the sound quality of the earbuds that
come with most portable players nowadays. On an
interesting note, I’ve found that the
“in-head” sensation typically
associated with headphones seems to be less pronounced with the Bose.